Desenvolvimento e avaliação de um protótipo a baixo custo para detecção de estresse hídrico na berinjela

Abstract

The indicators of the water status of the plants can be used in several situations. However, most of these indicators are determined by the use of expensive equipment, often through time-consuming techniques. Thus, the use of infrared thermometry presents itself as a great alternative, being of low cost and high practicality in the determination of water stress in plants. The objective of this work was to evaluate if the estimated water stress index of the crop (CWSI), calculated through the vapor pressure deficit (VDP), leaf temperature (Tc), air temperature (Tar) and relative humidity (UR), can be used as an indicator of water stress for the eggplant crop, and evaluate if there is a need to calculate the CWSI measured from the wet leaf temperature (Tw), comparing with the estimated CWSI and verify if there is a relation between the CWSI estimated, water potential, soil moisture and growth parameters. The experiment was conducted in a greenhouse at the Centro Estadual de Pesquisa em Agricultura Orgânica (PESAGRO) localizado no município de Seropédica – RJ. The culture was planted with eggplant (Solanum melongena L.), hybrid Nápoli, cultivated in 18 L pots, filled with a mixture of sandy clay loam soil and 20% of commercial substrate, spaced 0.70 x 1.0 m , arranged in 6 rows and with 7 pots each. The irrigation system used was located by drip irrigation. The plants were randomly assigned to two treatments. T1 and T2. Where T1 represents the plants that were maintained near the field capacity and T2 representing the plants that underwent water stress. The plants were submitted to seven cycles of stress, lasting between two and three days, varying according to the climatic conditions. All plants were kept close to field capacity, starting the cycle. Soon irrigation was suspended in T2, and T1 was always kept close to field capacity. After T2 suffered the water deficit, irrigation was resumed in all plants for at least two days before starting a new cycle. In order to establish an estimated CWSI correlation, the variables soil moisture and leaf water potential were evaluated. It was possible to verify that there is a satisfactory fit between the interval (Tc - Tar) and the VDP, which means that there is no need to measure Tw when it is possible to calculate VDP. The relationship between CWSIest and CWSImed obtained performance from the pet model rated "Very Good". Therefore, the CWSIest, using data from the prototype at low cost, can be used as an indicator of water stress for the eggplant crop. As the soil moisture decreased, the CWSIest presented relatively higher values. For the water potential, the CWSIest increased as it decreased, concluding that it is possible to use the prototype to detect the water deficit in the eggplant.